Many implementations of robotic platforms have been developed over the years. Most require human operation and are tethered or wired to a controller. This limits the platform's work area and applicability to particular tasks. A navigation system that allows a mobile robotic platform to operate autonomously in a relatively large work area for varied applications is preferable.
In the prior art, radio frequency (RF) based navigation systems have been utilized, such as the Global Positioning System (GPS). GPS is a system that transmits pseudo-noise (PN) signals from a constellation of orbiting satellites down to earth. Detection of these signals allows an earth-based receiver to determine ranges (distances) to the satellites. In fact, PN ranging is a standard technique in RF based navigation systems.
A problem with using RF based navigation systems involves their level of accuracy. Because the speed of radio propagation is roughly 10.sup.9 ft/sec, it is difficult to acquire precise range values. For instance, one inch ranging precision in RF based navigation systems requires sub nanosecond timing precision. That type of timing would be very difficult and expensive to incorporate into a navigation system. A GPS system is actually able to place an object within about 10 or 15 yards anywhere on earth. For a robotic application within a bounded area, this degree of accuracy is insufficient.
Alternatively, ultrasound has been used for navigation in various industrial applications. Ultrasonic frequencies are those above 20 kHz. Because high frequency sounds are attenuated rapidly in the air, ultrasound has an effective range of only about fifty feet. Thus, for applications requiring a platform to autonomously travel within an area of 200-300 yards, ultrasound is ineffective.
An object of the present invention is to provide a local area acoustic ranging/positioning system for an independent autonomous robotic platform without any wiring or tethering which results in accuracy greater than systems of the prior art.
An additional object of the invention is to provide a robotic platform that can accommodate a variety of work elements (tools) to adapt to a range of indoor and outdoor applications such as painting parking lots, marking and decorating athletic fields and autonomous surveillance.